This work examines pharmacology and drug safety through a systematic discussion of abnormal or adverse reactions occurring during therapeutic treatment. Written by Harry L. Alexander and published in 1955, the book reflects mid-twentieth-century medical concern with identifying and understanding adverse drug effects in clinical practice. The text likely analyzes mechanisms, documented case observations, and physiological responses associated with pharmaceutical therapies. Organized as a professional medical study, it aims to assist physicians in recognizing unexpected reactions, evaluating risks, and improving treatment decisions. Within the context of clinical pharmacology, the volume contributes to early discussions on drug monitoring, patient safety, and the responsible use of medications in therapeutic settings.